This invention relates to an apparatus for froth flotation and more particularly to an improved means for generating and skimming froth in a froth flotation cell.
In froth flotation, an aqueous pulp of a comminuted mineral aggregate is subjected to aeration or the like in the presence of one or more flotation reagents with the result that a mineral-bearing froth is formed on top of the pulp. In order to provide efficient removal and collection of the froth, it is necessary to skim the froth from the surface of the liquid in the flotation tank.
Many froth flotation systems have been developed in order to improve froth generation as well as froth collection. For example, U.S. Pat. No. 1,557,369 discloses a froth flotation apparatus employing stationary and rotary spirally curved skimming elements for skimming off froth in an attempt to remove the froth without deteriorating it.
U.S. Pat. No. 2,311,527 discloses a froth flotation cell having a flotation chamber and a skimming means in the form of a helical blade rotatably mounted on a horizontal axis. It is stated that the helical paddle skimmer removes the froth from the top of the pulp much more efficiently than the flat paddle type. Other U.S. patents which disclose skimmer devices include U.S. Pat. Nos. 4,462,909, 3,864,257, 2,922,521 and 838,626.
Particularly suitable froth flotation apparatus especially useful for the beneficiation of coal are disclosed in U.S. Pat. No. 4,347,126 and U.S. Pat. No. 4,347,127. These patents disclose flotation apparatus wherein primary spray nozzles are positioned above the flotation tank for spraying input slurry and recycle spray nozzles are positioned above the tank for respraying particulate matter collected in collection troughs positioned in the tank for collecting sinking material. The spraying operation creates a froth on the water surface in the flotation tank in which a substantial quantity of particulate matter is floating. The froth is then skimmed from the water surface, e.g. by a skimming arrangement in which an endless conveyor belt carries a plurality of spaced skimmer plates depending therefrom.
While many froth flotation apparatus and skimming arrangements are known, improved flotation cells and skimming arrangements which are more efficient and which will still provide adequate beneficiation results are still desired.